In manufacturing electronic devices, openings (e.g., trenches or holes) may be formed in an etching target layer due to etching of the etching target layer in some cases. In general, when the etching target layer contains silicon, plasma of a fluorocarbon gas is generated to etch the etching target layer. The etching target layer is etched by active species of fluorine and/or fluorocarbon from the generated plasma. The etching of the etching target layer using the plasma of fluorocarbon gas is described in Japanese Patent Laid-Open Publication Nos. 2013-098193 and 2006-269879.
Further, Japanese Patent Laid-Open Publication Nos. 2013-098193 and 2006-269879 describe that a focus ring is disposed to surround an edge of a workpiece including the etching target layer. The purpose of using the focus ring is generally to enhance the in-plane uniformity of the etching.
Further, Japanese Patent Laid-Open Publication No. 2013-098193 describes that a metal-made mask is formed on the etching target layer, and a pattern of the mask is transferred to the etching target layer by etching.